Relationship between certain physical and chemical properties and subsoil friability in Lemnos loam

Abstract

Lemnos loam, a red-brown earth used for fruit production in the Goulburn Valley, Victoria, has degrees of friability in the subsoil as assessed in the field. Forty-one samples from three subsoil depths were obtained from 25 sites near Kyabram. Aggregate stability, as measured in the laboratory was found to be related to field assessments of friability. Exchangeable cations, pH, silt, clay and clay minerals were determined on the samples. By relating some of these measurements to aggregate stability it has been shown that exchangeable Ca++ contributes to a strongly aggregated soil (friable) ; and silt, exchangeable Na+ and exchangeable Mg++ to a weakly aggregated soil (less friable). The effect of silt and exchangeable Na+ is greater than that of exchangeable Ca++ and exchangeable Mg++. A multiple regression equation describing the effect of these four significant factors on stability percentage is presented. This equation accounts for 85.5 per cent of the variation in stability percentage. There is a strong relationship between field assessment of friability and exchangeable Ca++/Mg++ ratio; the higher the ratio, the more friable is the soil.